Without limiting the scope of the invention, its background is described in connection with a downhole apparatus and method used in hydrocarbon production, and in particular to a downhole apparatus and method that improves the rate of production of hydrocarbons using a combination of artificial-lift techniques.
During the process of hydrocarbon production the natural pressure of a reservoir eventually decreases to the point that the pressure in the reservoir may become too low to force fluid from the producing zone to the surface. In response to this reduced pressure artificial-lift techniques may be required. In addition, artificial-lift techniques may be used at the onset of production, depending upon the characteristics of the reservoir. An artificial-lift system is defined as any system which adds energy to the fluid column in a wellbore, with the objective of initiating and improving production from the well. Artificial-lift methods fall into two groups, those that use gas and those that use pumps.
Artificial-lift methods that use pumps have a surface power source to drive a downhole pump assembly to generate a large positive pressure gradient between the exit point of the pump and the surface to increase the rate of fluid transport to the surface. In addition, a downhole pump reduces the pressure between the pump entry point and the wellbore interface with the reservoir to increase the differential pressure between the reservoir and the wellbore to increase the rate of fluid flow into the wellbore. There are several types of specialized downhole pumps in use, e.g., sucker-rod pump (SRP), electrical submersible pumps (ESPs) and progressive cavity pumps (PCPs). All of these pumping systems have a downhole pump that pushes fluid gathered in the wellbore in an upward direction. The fluid that flows from the reservoir into the wellbore usually consists of liquid (oil and/or water), gas and it is not uncommon for some amount of sand and other abrasive solids to be present in the production fluid.
U.S. Pat. No. 8,672,033, entitled, “Method of Improving Performance and Efficiency of Wellbore Pump for Hydrocarbon Production,” discloses a method of improving performance or efficiency of a wellbore pump associated with a wellbore and/or for increasing the rate of production of reservoir fluid from a reservoir, in which a wellbore pump is arranged to pump wellbore fluid within the wellbore to a surface. The method includes (a) selecting a wellbore which includes an associated wellbore pump associated with a production tube and arranged within a casing. An annulus is defined as the space between the casing and the pump/production tube. The annulus will ideally fill with reservoir fluid which has a hydrostatic head above the level of an inlet of the wellbore pump.